var person = { name: 'Bob', age: 20, tags: ['js', 'web', 'mobile'], city: 'Beijing', hasCar: true, zipcode: null };
JavaScript对象的键都是字符串类型,值可以是任意数据类型。上述
person
对象一共定义了6个键值对,其中每个键又称为对象的属性,例如,person
的name
属性为'Bob'
,zipcode
属性为null
person=new Object(); person.firstname="Bill"; person.lastname="Gates"; person.age=56; person.eyecolor="blue";
<!DOCTYPE html> <html> <body> <script> function person(firstname,lastname,age,eyecolor) { this.firstname=firstname; this.lastname=lastname; this.age=age; this.eyecolor=eyecolor; } myFather=new person("Bill","Gates",56,"blue"); document.write(myFather.firstname + " is " + myFather.age + " years old."); </script> </body> </html> >>> Bill is 56 years old.
<!DOCTYPE html> <html> <body> <script> function person(firstname,lastname,age,eyecolor) { this.firstname=firstname; this.lastname=lastname; this.age=age; this.eyecolor=eyecolor; this.changeName=changeName; function changeName(name) { this.lastname=name; } } myMother=new person("Steve","Jobs",56,"green"); myMother.changeName("Ballmer"); document.write(myMother.lastname); </script> </body> </html> >>> Ballmer
对象变量.属性名
的方式,但这要求属性名必须是一个有效的变量名。如果属性名包含特殊字符,就必须用''
括起来:对象名[属性名]
的方式来访问var xiaohong = { name: '小红', 'middle-school': 'No.1 Middle School' }; xiaohong['middle-school']; // 'No.1 Middle School' xiaohong['name']; // '小红' xiaohong.name; // '小红'
undefined
'use strict'; var xiaoming = { name: '小明' }; console.log(xiaoming.name); console.log(xiaoming.age); // undefined
var xiaoming = { name: '小明' }; xiaoming.age; // undefined xiaoming.age = 18; // 新增一个age属性 xiaoming.age; // 18 delete xiaoming.age; // 删除age属性 xiaoming.age; // undefined delete xiaoming['name']; // 删除name属性 xiaoming.name; // undefined delete xiaoming.school; // 删除一个不存在的school属性也不会报错
xiaoming
是否拥有某一属性,可以用in
操作符:var xiaoming = { name: '小明', birth: 1990, school: 'No.1 Middle School', height: 1.70, weight: 65, score: null }; 'name' in xiaoming; // true 'grade' in xiaoming; // false
in
判断一个属性存在,这个属性不一定是xiaoming
的,它可能是xiaoming
继承得到的'toString' in xiaoming; // true
因为
toString
定义在object
对象中,而所有对象最终都会在原型链上指向object
,所以xiaoming
也拥有toString
属性。
xiaoming
自身拥有的,而不是继承得到的,可以用hasOwnProperty()
方法:var xiaoming = { name: '小明' }; xiaoming.hasOwnProperty('name'); // true xiaoming.hasOwnProperty('toString'); // false
var test = 'test'; test.length >>> 4
var message="Hello world!"; var x=message.toUpperCase(); x >>> "HELLO WORLD!"